Digital deformities are among the most common forefoot pathologies encountered by podiatrists and orthopedic surgeons. Digital deformities may occur in the form of hammertoes, claw toes, mallet toes, bone spurs, overlapping and underlapping toes, mallet fingers, jersey fingers, and coach's fingers, among others. The deformities typically affect the interphalangeal joints of the hand or the foot, metatarsophalangeal joints of the foot, or metacarpophalangeal joint of the hand. Digital deformities in the fingers or toes result from imbalance of the tendons, causing them to stretch or tighten abnormally. These deformities may be either congenial or acquired. For example, the deformities may be cause by neuromuscular and arthritic disorders, systemic diseases, flat or high-arched feet, or traumatic injuries to the joints. Toe deformities can also be aggravated by poorly fitting footwear.
Hammertoe, for example, results in a bend in the middle joint of the toe into a claw-like deformity. While at first the patient may be able to move and straighten the toe, overtime the hammertoe may become fixed. In this contracted position, the inside of the shoe rubs against the contracted joints, causing corns to form on the top of the toe and calluses to form on the sole of the foot. In certain patients these corns and calluses may open or ulcerate and form wounds. This causes pain and discomfort in walking or wearing shoes. FIG. 1A depicts a human foot 100 afflicted with hammertoe deformity. Distal phalanx 101, middle phalanx 103, proximal phalanx 105, and metatarsal 107 bones are depicted in foot 100. The distal interphalangeal joint 104 is formed between the distal 101 and middle 103 phalanges, proximal interphalangeal joint 106 is formed between the middle 103 and proximal 105 phalanges, and the metatarsophalangeal joint 108 is formed between the proximal phalanx 105 and the metatarsal 107. The hammertoe deformity in the foot is apparent in the proximal interphalangeal joint 106.
A similar digital deformity condition in the hand is depicted in FIG. 1B. FIG. 1B depicts a human hand 110 afflicted with mallet finger deformity. Distal phalanx 111, middle phalanx 113, proximal phalanx 115, and metacarpal 117 bones are depicted in hand 110. The distal interphalangeal joint 114 is formed between the distal 111 and middle 113 phalanges, the proximal interphalangeal joint 116 is formed between the middle 113 and proximal 115 phalanges, and the metacarpophalangeal joint 118 is formed between the proximal phalanx 115 and the metacarpal 117. The mallet finger deformity in the hand is apparent in the distal interphalangeal joint 114.
Early treatments for digital deformities include the use of strapping, taping, orthotics, or immobilization of the hand or the foot. However, once the deformity becomes fixed, surgical treatment will be necessary. Surgical treatments include bone fixation devices that fixate the bones in order to fuse them into a stable mass. These orthopedic implant devices realign bone segments and hold them together in compression until healing occurs, resulting in a stable mass. Typical implant devices include intramedullary nails, plates, rods and screws.
Infection and complications are a major concern in these procedures. Wound closure is technically demanding for the surgeon, and devices that add surface prominence, such as plates or exposed screws, add to the difficulty by requiring greater tissue tension during incision reapproximation. This increases the risk of post-operative wound infections and dehiscence that may ultimately result in limb amputation. While there exist less intrusive devices, many devices lack the application of compression forces to the bone, causing the treated bones to eventually become misaligned from the desired position.
There is therefore a need for improvements in intramedullary fixation implants and methods of use that overcome some or all of the previously described drawbacks of prior fixation assemblies and processes.